National foreword

This British Standard is the UK implementation of ISO 7544:2024.

The UK participation in its preparation was entrusted to Technical Committee MCE/7, Rolling bearings.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 September 2024.

Foreword

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The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of ISO document should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

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This document was prepared by Technical Committee ISO/TC 4, Rolling bearings.

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

Introduction

This document is based on ISO 16232. However, the inspection and evaluation methods in ISO 16232 cannot be directly transferred to the rolling bearings industry, because of the different uses of rolling bearings in a wide variety of applications. This document has been prepared to describe a common and general approach for the inspection of cleanliness of rolling bearings.

The cleanliness requirements on rolling bearings increase steadily. The cleanliness of rolling bearings has a direct influence on achieving reliable performance, especially in association with vibration and noise, as well as the life of rolling bearings according to ISO 281. Therefore, the cleanliness of rolling bearings is necessary to a certain level. Various test and assessment methods of rolling bearing cleanliness lead to differences in inspection and assessment results. To avoid incomparable inspection results, the extraction procedure, the test fluid and the parameter settings for the test equipment are described in this document.

Figure 1 shows that the type of contaminant particle is crucial in determining the particle size and counting. After several times of over rolling, brittle particles break into small pieces as shown in Figure 1 a); in comparison to the measured thickness, their effective size is reduced significantly. Ductile particles can be deformed as shown in Figure 1 b).

Particulate contaminants (debris), entrapped into the contact between the rolling elements and the raceways, are the main cause for surface-initiated damages, which produce many rolling bearings failures. Subject to the elastic properties of the rolling element and raceway materials, entrapped particles, under the heavily loaded contacts, deform mainly in the inlet zone and remain nearly the same as they pass through the Hertzian contact zone, leaving the indentations on the mating surfaces. It seems clear that brittle particles, like corundum (Al₂O₃) and silicon carbide (SiC), tend to fracture and break into smaller pieces during the entrainment into the contact. Ductile particles, like copper, plastics and textile fibres are heavily deformed during the entrainment and extruded subsequently from the contact, as shown in Figure 1; see Reference [9] for further information.

This document does not give the cleanliness limits for rolling bearings. The cleanliness required for a specific application is dependent on many factors. Cleanliness limits can be agreed between the supplier and customer.

1 Scope

This document specifies procedures and equipment for cleanliness inspections of rolling bearings. It describes, in particular, test methods and assessment techniques.

This document is applicable to the test and assessment of various types of open bearings and capped bearings before grease filling, as well as the test and assessment of rolling bearing parts.

This document is not applicable for linear motion rolling bearings.

2 Normative references

3 Terms and definitions

4 Symbols and abbreviated terms

5 Main steps of cleanliness inspection

6 Equipment and accessories

6.1 Equipment for extraction

6.2 Equipment for filtration

6.3 Auxiliary accessories

6.4 Equipment for analysis

7 Blank value

8 Test lot

8.1 General

8.2 Test lot size

9 Extraction

9.1 General

9.2 Test fluid

9.3 Pressure-rinsing method

9.4 Ultrasonic method

10 Filtration and drying

10.1 General

10.2 Analysis filter

10.3 Procedure for filtration

10.4 Procedure for drying

11 Analysis

11.1 Gravimetry

11.2 Light-optical analysis

12 Test report

13 Escalation

Bibliography

BS ISO 7544:2024

Rolling bearings. Test and assessment methods for cleanliness

Current

Published:

30 Sep 2024